N1-(5-chloropyridin-2-yl)-N2-((1S,2R,4S)-4-[(dimethylamino)carbonyl]-2-{[(5-methyl-4,5,6,7-tetrahydrothiazolo[5,4-c]pyridin-2-yl)carbonyl]amino}cyclohexyl)ethanediamide p-toluenesulfonic acid monohydrate represented by the following formula (A) (hereinafter, also referred to as compound A):
is known as a compound that exhibits an inhibitory effect on activated blood coagulation factor X (FXa), and is useful as a preventive and/or therapeutic drug for thrombotic diseases (Patent Literature 1 to 8).
For example, a method comprising mixing the free form of compound A represented by the following formula (B) (hereinafter, also referred to as compound B):
with p-toluenesulfonic acid or p-toluenesulfonic acid monohydrate, followed by crystallization from aqueous ethanol, is known as a method for obtaining compound A (Patent Literature 1 to 8). These literature documents do not make any mention about adding p-toluenesulfonic acid or p-toluenesulfonic acid monohydrate in a stepwise manner in the step of obtaining compound A from compound B.